Wear compensator



June 20, 1961 G. A. WALKER ET AL 2,989,166

WEAR COMPENSATOR 4 Sheets-Sheet 1 Filed May 2, 1960 INVENTORS GEORGE A. WALKER RONALD D. DODGE F GE LEON E. PALMER ATTORNEY.

n 20, 1961 G. A. WALKER ETAL' 2,989,166

WEAR COMPENSATOR Filed May 2, 1960 4 Sheets-Sheet 2 FIG. 2

FIG. 4

June 20, 1961 WALKER ET AL 2,989,166

WEAR COMPENSATOR 4 Sheets-Sheet 3 Filed May 2, 1960 June 20, 1961 WALKER ET AL 2,989,166

WEAR COMPENSATOR Filed May 2, 1960 4 Sheets-Sheet 4 FIG. 5

UNITS 0F MOVEMENT 2,989,166 WEAR 'COIVIPENSATOR George A. Walker, Ronald D. Dodge, and Leon E. Palmer, Lexington, Ky., assignors to International Business Machines Corporation, New York, N.Y., a "corporation of New York lh'led May 2, 1960, Ser. No. 26,151 6Claims. (Cl. 197--16) This invention is directed to wear compensating devices, and more particularly to devices which operate automatically to compensate for wear in mechanisms which move a print element to different printing positions.

In US. Patent No. 2,919,002 issued to L. E. Palmer there is shown a typewriter having a single element which is movable to different positions for printing any one of various characters. The print element is generally of a spherical shape and its positioning mechanism includes means for rotating the element in either direction from a home position a distance of one to five units. Any suitable detenting means such as that shown in US. Patent No. 2,926,768 issued to L. E. Palmer et al. may be used for accurately locating the print element in each of its printing positions. This detenting means will compensate for slight inaccuracies in adjustment of the positioning mechanism and for slight wear between its operating parts. If nothing more is provided, a manual adjustment of the positioning mechanism becomes necessary as soon as the inaccuracy in the positioning of the element exceeds the compensation that may be obtained from the detenting means. By providing in the positioning mechanism a device which automatically adjusts itself to compensate for wear, a much longer period of operation may be obtained before any manual adjustment is necessary.

An object of this invention is to provide an improved wear compensating device.

Another object is to provide in a positioning mechanism for a print element, a device which automatically adjusts itself to compensate for wear between operating parts of the mechanism.

Still another object is to provide a wear compensating device including a pair of pivoted members which normally operate together but which assume new positions relative to each other when wear takes place.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a view of a printing mechanism having the improved compensating device embodied therein.

FIG. 2 is a perspective view of a printing head and means for rotating it from a home position.

FIG. 3 is a perspective view of an exploded compensating device.

FIG. 4 is an enlarged side elevational view of a portion of the compensating device.

FIG. 5 is a diagrammatic view indicating operating parts of the compensating device in different positions.

There is shown in the drawings a typing mechanism like that of Patent No. 2,919,002 except for a wear compensating device 1 (FIG. 1) connected between a link 2 and a flexible tape 3 which is actuated to effect rotation of a printing head 4. One end of the link 2 is connected to a bellcrank 5 which is pivotally supported at 6 and has an arm pivotally connected to a member 8 forming part of a drive mechanism generally designated 10. Included in the mechanism 10 are selecting links 11 and 12 which are hook-shaped at their lower ends and are connected at their upper ends to a floating member 14 in such a way that they may swing forwardly relative to the member and also ice permit pivotal movement of the latter about either connection. A link 16 pivotally connects the member 14 to one end of another floating member 18 which is connected by a link 19 to one end of the member 8. Another selecting link 20 is connected to the opposite end of the member 18 and has a hook shaped portion at its lower end. The other end of the member 8 is pivotally connected to a link 22 which is normally held in the position shown but may be moved a predetermined distance to a higher position.

During a printing operation, one or more of the operating links 11, 12 and 20 are swung forwardly to position their hooked portions under a bail 24 which is caused to rock downwardly. The connections between the members 14, 18 and the links 16, 19 are such that a movement of the selecting link 11 downwardly with the bail causes the bellcrank 5 to rotate one unit in -a counterclockwise direction. Movement of either link 12 or link 20* downwardly with the bail causes the bellcrank to rotate two units in a counterclockwise direction. When two or more links are moved with the bail, the bellcrank rocks a distance equal to the sum of the distances obtained by movement of the individual links.

As the bellcrank 5 rocks counterclockwise, the compensating device 1 swings about a shaft 25 and pulls on the tape 3 to cause a rotation of the printing head 4 in a clockwise direction. Referring to FIG. 2 it will be noted that tape 3 is connected at one end to a carrier 26 for the head 4, then extends around a pulley 27 on the device 1, a pulley 28 supported by an arm 29 and a pulley 30 operatively connected to the printing head. After making approximately one turn around the pulley 30, the end of the tape is connected thereto by any suitable means not shown. At the lower side of pulley 30 is a helical spring 31 which tends to rotate the pulley in a counterclockwise direction. Formed on the printing head are vertical rows of characters, and a rocking of the bellcrank 5 one unit distance causes a turning of the head a distance equal to the spacing between adjacent rows of characters.

The spring 31 acting on the printing head tends toswing the upper end of the compensating device 1 to the right in FIG. 1. This places a tension on the link 2 tending to rotate the bellcrank 5 in a clockwise direction. Bellcrank 5 acting through member 8 on link 22 tends to raise the latter from the position shown. As described in Patent No. 2,919,002, the link 22 is normally latched in its lower position but may be unlatched so it follows a cam, not shown, to a raised position. When the link 22 is permitted to move to its raised position, the bellcrank rocks clockwise a distance of five units and perm-its the printing head to turn counterclockwise a corresponding distance. If the selecting links 11, 12 or 20 are actuated simultaneously with the lifting of the link 22, the bellcrank is rocked clockwise a distance equal to five units minus the distance obtained by the actuation of the selecting links. It will be noted that any wearing of the mechanisms operating on the bellcrank 5 will cause the latter to turn a proportional distance in a clockwise direction. This will cause the print head to rotate slightly so its rows of characters are offset a little from correct printing positions. Any wear on the bellcrank, the link 2 and operating parts of the device 1 will have the same effect on the printing head. The device 1 is so designed as to compensate for any Wear when the bellcrank is rotated clockwise five units.

As shown in FIGS. 1 and 3, the device 1 comprises a pair of arms 35 having openings 36 adjacent their lower ends for receiving the shaft 25. Spacers 37 and 38 have reduced portions at their ends extending through open ings 39 and 40 in the side arms. The outer ends of the reduced portions are headed over for holding the arms in proper spaced relationship and for connecting the arms to pivot as a unit about the shaft 25. Formed on the shaft is an enlarged portion 42 providing a shoulder 43 which engages one of the arms 35 when the shaft 25 is fully extended through the openings 36. A C-clip 45 engages a slot 46 in the shaft for holding the arms in place. The pulley 27 is rotatably supported by a bolt 47 extending through openings 48 at the upper ends of the arms. Projecting from the head of the bolt is an eccentric portion 50 which is engageable with a stop member 51 (FIG. 4) attached to a side plate 52 on the machine. As shown herein, the stop member is in the form of a spring arm attached at its lower end to the plate 52 and bent outwardly for engagement by the eccentric portion as the arms 35 move through their fifth unit of travel. When the arms 35 have pivoted clockwise a distance permitting rotation of the head 4 coutnerclockwise to the fifth row of characters from its home position, the stop member may engage the plate 52 or some other abutment for preventing further movement of the arms. Attached to the side plate 52 is a U-shaped bracket 54 which supports the shaft 25.

Located between the arms 35 is a member 56 having an eccentric hub portion 57 containing an opening 58 through which the shaft 25 extends. Formed on the member 56 is an arm 68 engageable with an eccentric stop member 61 (FIG. 1) which is adjustably attached to the arms 35 through openings 62. Another arm 63 on the member 56 is connected by a spring 64 to the spacer 38 for urging the member about the shaft in a clockwise direction until its arm 60 engages the eccentric 61. Member 56 is also provided with a finger 66 which engages the bracket 54, FIG. 1, after it rotates a predetermined distance in a clockwise direction. The adjustment of the eccentric 61 is such that a clearance of approximately .005 of an inch exists between the finger 66 and the bracket 54 when the arms 35 have been rotated a distance of four units in a clockwise direction from their home position. When the arms are rotated five units, the finger 66 engages the bracket 54 soon after a rotation of four units and holds the member 56 stationary while the arms continue to rotate through the remaining portion of the fifth unit. As wear in the operating mechanisms takes place, the arms 35 turn a corresponding distance in a clockwise direction and cause the finger 66 to engage the bracket 54 earlier in the fifth unit of movement.

Located between the arms 35, as shown in FIG. 3, is a member 68 having an opening 69 which receives the hub portion 57 on the member 56. Surrounding the opening 69 is a sleeve portion 70 extending through a slot 71 in a member 72 with a sliding fit. The slot 71 has a lower portion 73 of reduced width for receiving a bolt 74 which extends through an opening 75 in the member 68. Bolt 74 connects the members 68 and 72 together for operation as a single lever, generally designated 76. When the bolt 74 is loosened, the member 72 may be moved radially of the opening 69 for varying the length of the lower lever arm. Extending from the member 68 is an arm 77 which is connected by a spring 78 FIG. 1) to the spacer 38 for urging the lever 76 in a counterclockwise direction about the hub portion 57 relative to the arms 35.

Formed in each of the arms 35 is a slot 80 communicating at its lower end with a larger opening 81. A roller 82 operates within the slot 80 as a stop for limiting pivotal movement of the lever 76 in a counterclockwise direction relative to the arms 35. This roller comprises a cylindrical portion 83 which fits loosely within the slot 89, and integral head portions 84 which pass through the openings 81 but act on the outer surfaces of the arms 35 for holding the roller in place when its portion 83 is moved into the slot 80. Formed on the member 68 adjacent the slot 80 is a surface 86 which is inclined relative to the sides of the slot. As shown in FIG. 1, the surface 86 is so inclined that its lower end lies nearer the center line of the slot 80 than does its upper end. Some point on the surface 86 always engages the portion 83 on the roller 82 for limiting movement of the lever 76 relative to the arms 35 in a counterclockwise direction. A movement of the lever 76 in a clockwise direction relative to the arms results in a dropping of the roller 82 within the slot for holding the lever in a new position relative to the arms. The link 2 is connected to the lower end of the member 72 forming part of the lever 76. Arms 35 are continuously urged in a clockwise direction due to the tension placed on the tape 3 by the spring 31 tending to rotate the printing head 4. This causes the roller 82 to act on the lever 76 for urging the latter in the same direction. Lever 76 is also urged in a clockwise direction by a spring 87 connected to the machine frame. The link 2 and the drive mechanism associated therewith permit the lever 76 to swing unit distances in this direction from a home position only when certain characters are to be printed.

The wear compensating device 1 is initially adjusted so that a movement of the link 2 to the left from one to four units will cause the arms 35 to swing distances which effect rotation of the printing head from one to four character positions. This is accomplished by shifting the member 72 until the lower arm of the lever 76 is of the proper length to give the desired angle of swinging motion. The eccentric portion 50 is adjusted so it engages the stop member 51 at approximately the time when engagement between the finger 66 and the bracket 54 takes place. During this time, the roller 82 is located at the upper end of the slot 80. The eccentric 61 is adjusted so a clearance of approximately .005 inch exists between the finger 66 and the bracket 54 when the lever 76 rotates four units in a clockwise direction. The eccentric hub portion 57 is so formed that the lever 76 turns about a center located directly below the axis of the shaft 25 when the member 56 is held against rotation.

The operation of the wear compensating device 1 is as follows: Assuming that the adjustments mentioned above have been made, movements of the link 2 to the left will result in a swinging of the arms 35, the lever 76 and the member 56 in a clockwise direction about the axis of the shaft 25. This continues until the finger 66 engages the bracket 54 and stops further rotation of the member 56. As mentioned above, this engagement takes place just after the link 2 has moved four units. There is shown in FIG. 5 a representation of the device '1 in different positions. The line A-B represents the positions of the arms and the lever 76 before any movement of the link 2 to the left takes place. While the link moves a little over four units to the left, the mechanisms of line AB swing about a point x on the axis of the shaft 25 to the position A1, B-l. At this time, the finger 66 engages the bracket 54 and stops the member 56 so that further swinging of the lever 76 in a clockwise direction takes place about the point Y at the center of the hub 57. Since the lower arm (A1)-Y of lever 76 is now shorter than it was and its upper arm Y-(B1) is longer, the upper end of the lever 76 tends to move more rapidly than it did before the member 56 was stopped. The spring member 51 retards its motion, however, so it travels at approximately the same speed it did before.

As the compensating device swings from the position of line A-B to that of line (A1)(B1), the link 2, the mechanism 10, and parts of the compensator 1 are subjected to the action of springs 31 and 87. There is some elongation and bending of parts under this load. As the eccentric portion 50 engages the spring stop member 51 and flexes the latter until the arms 35 are stopped at point B-2, the load on the operating mechanisms is reduced permitting the system to contract. With the action of the spring 31 completely removed when the upper ends of the arms 35 reach point B-2, the system is so contracted that the lower end of the lever 76 lies at point A-2 when the link 22 is at its uppermost position. Spring 87 maintains a fixed tension on the system so its operating parts always act on each other at the same surfaces. As wear on different parts of the mechanisms take place, the lower end of the lever 76 moves a corresponding distance to the left. This means that the printing head will be offset slightly from its correct printing positions as the lever 76 is operated during movement of the link 2 from one to four units to the left. The fifth printing position will be correct, however, since the member 51 stops movement of the arms 35 at that position. With some wear in the system and the link 2 moved-four units to the left, the finger 66 lies closer to the bracket 54 than the .005 of an inch mentioned above. As the link moves further to the left, the finger 66 engages the bracket 54 earlier in the fifth unit of movement than it did when no wear existed. The engagement still takes place when the lower end of the lever 76 is moved to the position A-1 in FIG. 5. Movement beyond this position results again in the swinging of the lever about point Y. When the lower end of the lever reaches point A-Z, the arms 35 are stopped by the member 51 and'the system is contracted due to its removal from the action of spring 31. This point is reached, however, before the link 22 reaches the upper position to which it is permitted to move. The spring 87 acts to swing the lever 76 for forcing the bellcrank 5 in a clockwise direction until the link 22 reaches its uppermost position. During this time, the lever 76 turns in a clockwise direction relative to the arms 35 and permits the roller 82 to drop in the slot 80 for engaging the surface 86 at a lower point. As the link 2 moves again to the right, the lever 76 is rotated counterclockwise and causes the arms 35 to swing with it due to its action on the roller 82. The positions of the lever 76 and the arms 35 relative to each other are different, however, due to the movement of the roller to a lower position. on each operation of the mechanism to turn the printing head five units in a counterclockwise direction from its home position, the device I automatically adjusts itself as described above to compensate for any wear that has taken place. When total wear becomes great enough to permit movement of the roller to the lower end of the slot 80, manual adjustments are made to effect a correct positioning of the printing head when the roller is again located at the upper end of the slot 80. The device 1 may then continue to make compensations as further wear takes place.

The forming of characters on the printing head may be such that any normal typing operation will result in a turning of the head from time to time in a counterclockwise direction five units. An operation of the device 1 to adjust itself will take place at this time if any wear exists.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A device for compensating wear in a mechanism which is operable to permit movement of a member from a home position under the action of yielding means, said device comprising, in combination, a lever, means supporting said lever for pivotal movement about a first axis through a predetermined angular distance and then about a second axis spaced from said first axis, an arm mounted for pivotal movement about said first axis, a roller, means supporting said roller on said arm for movement relative thereto in a fixed path under the force of gravity,

a surface on said lever engageable by said roller for limiting movement of said arm relative to said lever in one direction but permitting movement of said lever relative to said arm in the same direction, said surface being inclined relative to the path of movement of said roller so that any movement of said lever relative to said arm results in a movement of said roller to a new position in its path for holding said arm in a new position relative to said lever, means for connecting said lever to said mechanism, means for connecting said arm to said member, means for stopping said arm on reaching a maximum position to which it is permitted to move by said mechanism before wear takes place, and means for yieldingly urging said lever in the direction permitted by operation of said mechanism.

2. The device of claim 1 in which said second axis is spaced closer to the point of connection between said lever and said operating mechanism than said first axis.

3. The device of claim 1 in which said stopping means is first engaged by said arm at substantially the same time said lever starts to pivot about said second axis, said stopping means first yieldingly opposing movement of said arm and then bringing it to a stop at said maximum position.

4. The device of claim 1 in which the connections to said lever and said arm are such that both tend to pivot in the same direction under the action of said mechanism and said member.

5. A device for compensating wear in a mechanism which is operable to permit movement of a member from a home position under the action of yielding means, said device comprising, in combination, a lever, a support member, means pivotally mounting said support member on a first axis, a hub portion on said support member arranged eccentrically with respect to said first axis, an opening in said lever rotatably receiving said hub portion, an arm mounted for pivotal movement about said first axis, an abutment on said arm, a projecting portion on said support member engageable with said abutment, means yieldingly holding said support member in a position with its projecting portion engaging said abutment, a roller, means supporting said roller on said arm for movement relative thereto in a fixed path under the force of gravity, a surface on said lever engageable by said roller for limiting movement of said arm relative to said lever in one direction but permitting movement of said lever relative to said arm in the same direction, said surface being inclined relative to the path of movement of said roller so that any movement of said lever relative to said arm results in a movement of said roller to a new position in its path for holding said arm in a new position relative to said lever, means for connecting said lever to said mechanism, means for connecting said arm to said member, means for stopping said support member after predetermined movement of said lever under action of said mechanism, said lever then pivoting about said hub portion while said arm continues to pivot about said first axis, means for stopping said arm on reaching a maximum position to which it is permitted to move by said mechanism before wear takes place, and means for yieldingly urging said lever in the direction permitted by operation of said mechanism.

6. The device of claim 5 in which the eccentric hub portion on said support member provides a second axis closer to said mechanism than said first axis.

No references cited. 

